This invention relates generally to a reproducing machine, and more particularly concerns a system for advancing successive photosensitive members to an operative location in the reproducing machine after a predetermined interval of usage.
In a typical reproducing machine, as exemplified by an electrostatographic printing machine, a latent image is recorded on an insulating medium and developed with charged particles. A sheet of support material is positioned closely adjacent to the latent image and arranged to have the particles transferred thereto, in image configuration. After the particles are transferred to the sheet of support material, they are permanently affixed thereto forming a copy of the original document. Electrophotographic printing and electrographic printing are different versions of electrostatographic printing. In the process of electrophotographic printing, photoconductive insulating medium is sensitized and irradiated with a light image of an original document. The light image dissipates the charge on the photoconductive insulating medium in accordance with the intensity thereof. This records an electrostatic latent image on the photoconductive insulating medium corresponding to the original document being reproduced. Electrographic printing differs from electrophotographic printing in that an insulating medium is employed to form, without the aid of electromagnetic radiation, an electrostatic latent image for producing a viewable record.
In electrophotographic printing, the photoconductive insulating member is continually re-used. Generally, the photoconductive insulating medium is constructed from a photoconductive drum which continually recirculates. After an interval of usage, the photoconductive surface fatigues and does not recover satisfactorily. At this time, the drum must be replaced. Typically, a drum might be usable for thousands of copies. However, inevitably, the drum must be replaced. Recently, the photoconductive insulating medium has been made in the form of an endless web or belt. The belt configuration has numerous design advantages such as being incrementally advanceable so that successive new portions thereof may be periodically moved to an operative position. However, the typical belt or drum configuration is extremely difficult to replace. Moreover, the belt or drum frequently has used toner particles clinging thereto which increase the difficulty in handling during the removal thereof from the printing machine.
Some of these difficulties have been overcome by the prior art. For example, U.S. Pat. No. 3,619,050 issued to Swanke discloses an automatic endless photoconductive belt replacement system. This system uses a tow bar arrangement that engages slots in the leading and trailing edges of the replacement photoconductive belt. The tow bar grips the leading edge of the photoconductor at a replacement station and unwinds the photoconductor. It carries the photoconductor around a conveyor mechanism. Thereafter, it engages the trailing edge of the photoconductor. The photoconductor is then tensioned about the conveyor so as to secure it on a supporting mechanism. U.S. Pat. No. 3,877,806 issued to Schrempp et al. describes an apparatus for continually replacing increments of a photoconductive belt with fresh segments from a cartridge thereof. However, none of the prior art appear to teach the automatic replacement of successive photoconductive belts after a predetermined interval of usage. Moreover, there does not appear to be any teaching of a storage mechanism for housing a plurality of photoconductive members, each of which may be automatically advanced to the operative position in the electrophotographic printing machine.
Accordingly, it is a primary object of the present invention to improve reproducing machines by having a plurality of photoconductive members stored therein and advanced successively therefrom to the operative position after a predetermined interval of usage.